1. Field of Invention
The present invention relates to a position guiding technology, and more particularly to a web transportation guiding apparatus and method for guiding a position shift occurred during web transportation.
2. Related Art
FIG. 1 is a schematic view illustrating that a web has a shift. Since the web 90 has had a lateral shift δ during a winding, which causes a situation that the web 90 snakes when being unwound through a roller 10. An edge of the web 90 continuously shifts from a position of c towards a position of d during the unwinding, such that a lateral shift on the edge after the web 90 is unwound is exactly δ. The above situation is merely one of the causes for the snaking of the web. Moreover, the inconsistent parallelism between the rollers in a roll to roll equipment is a common reason why the web snakes. Therefore, a good edge tracing guiding module is needed to effectively solve the problem of the snaking of the web.
A swing-type edge tracing guiding apparatus available on the market is generally used during the web transportation, however, some problems cannot be directly alleviated in usage. Not because the usage of the swing-type edge tracing guiding apparatus has disadvantages, but the principle of the swing-type edge tracing restricts the overall guiding precision and response speed in some special situations. FIG. 2 is a schematic view of the swing-type edge tracing guiding apparatus. In the swing-type guiding apparatus in the prior art, the web shift must be compensated by rotating a specific angle for the swing-type edge tracing guiding apparatus. Therefore, when a tiny shift is to be compensated, a driving apparatus must have a higher angle resolution to compensate the tiny shift precisely.
In addition, in FIG. 2, for a sensor 11, the web before a critical line A has a tendency of shifting to the right. Therefore, when the web before the critical line A reaches the sensor, an included angle θ1 must be formed between the swing-type edge tracing guiding apparatus and the critical line A, so as to effectively maintain the edge position of the web at a reference O. However, it should be particularly noted that once the web after the critical line A reaches the sensor, since the web has a tendency of shifting to the left for the sensor, the swing-type edge tracing guiding apparatus must be driven immediately to form an included angle θ2 with the critical line A, so as to effectively maintain the edge position of the web at the reference O. It should be noted that the swing-type edge tracing guiding apparatus must be rotated by an angle of θ1+θ2 in an extremely short time, but the swing-type edge tracing guiding apparatus is hardly able to respond with a proper angle in time, such that the edge position of the web is deviated from the reference O.
FIG. 3 is a schematic view illustrating an error of a swing-type edge tracing guidance in the prior art. An edge position of a web 18 is measured by a sensor 24 that is generally placed between rollers 16 and 22, and a transportation reference of the web 18 is set at a position at a distance X from a point C. The roller 16 may swing left and right, so as to compensate the shift during the transportation of the web 18. As shown in FIG. 3, when a shift occurs to the web 18 during the transportation, an included angle D is formed between the roller 16 and the roller 22 in order to compensate the shift, and thus a deflection is generated in a region 28 between the rollers 16 and 22. Although the position of the web 18 detected by the sensor 24 has always been maintained at X, the position of the web 18 after leaving the roller 24 has been changed to Y due to a distance between the sensor 24 and the roller 22. Therefore, a compensation error δ is generated, and δ=X−Y.
In another guiding manner, a translation-type guiding apparatus is used, but a situation in which a moving travel 12 of a linear moving platform reaches a travel limit (as shown in FIG. 4A) may occur to the apparatus, such that the function of adjusting a shift of a web 90 is restricted. Moreover, a situation in which the web 90 shifts beyond a clamping range of a roller 13 (as shown in FIG. 4B) may occur to the translation-type guiding apparatus. The two situations often occur during the usage of the translation-type guiding apparatus. When encountering the above situations in FIGS. 4A and 4B, those of ordinary skill in the art often wrongly believe that the problems lie in an insufficient roller length or motor travel, and that the problems can be alleviated as long as the roller length or motor travel is increased. However, this is always not the case. Even if the roller length or motor travel is increased, the time points at which the above situations occur are delayed, but these problems cannot be solved effectively.
Furthermore, U.S. Pat. No. 7,267,255 has disclosed a web trace adjustment apparatus in which a driving wheel capable of adjusting a shift is disposed in a gimbal direction, so as to adjust a trace along which a web intends to move. U.S. Pat. No. 6,705,220 has disclosed a web trace adjustment apparatus in which a pair of movable angle bars is used to guide a moving web to enter into or move out of a transportation system.
Additionally, U.S. Pat. No. 6,124,201 has also disclosed a web guiding manner, in which a side edge position of a web is monitored, and the position of the web is guided by an upstream guiding apparatus if a shift is found. In addition, U.S. Pat. No. 4,958,111 and U.S. Pat. No. 4,453,659 have also disclosed an apparatus for adjusting a web position.